JP3941607B2 - Water treatment method and water treatment apparatus - Google Patents
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Description
【０００１】
【発明の属する技術分野】
本発明は、原水の凝集濾過処理に当たり、無機凝集剤の凝集補助剤として用いられる高分子凝集剤の添加量を適正に制御することにより、高分子凝集剤の過剰添加による濾過器又は濾過池等の濾過手段の差圧の急激な上昇を防止して、処理効果の向上及び安定化を図る水処理方法及び水処理装置に関する。
【０００２】
【従来の技術】
従来、浄水処理や排水処理において、原水中の懸濁物質（ＳＳ）を除去するために、原水にポリ塩化アルミニウム（ＰＡＣ）や塩化第二鉄などの無機凝集剤を添加して凝集沈殿処理した後、上澄水を更に濾過器や濾過池等の濾過手段で重力濾過又は圧力濾過することが行われている。また、凝集沈殿性の向上を目的として、無機凝集剤と共にノニオン性、アニオン性等の高分子凝集剤を併用することも行われている。この場合、一般的には、図２に示す如く、原水に無機凝集剤を添加して第１凝集槽１で凝集処理した後、高分子凝集剤を添加して更に第２凝集槽２で凝集処理することによりフロックを粗大化させ、その後、沈殿池３で沈降分離して上澄水を得、この上澄水を濾過器４等の濾過手段で濾過処理している。
【０００３】
従来、このような凝集濾過処理においては、濾過処理に先立つ凝集沈殿処理において、ＳＳを十分に沈殿分離し、濾過手段へのＳＳ負荷を低減することが、濾過手段の差圧上昇の防止及び濾過性能の維持、濾過手段の逆洗頻度の低減及びそれによる運転効率の向上、濾過手段寿命の延長等の面で望まれる。
【０００４】
従来においては、濾過手段へのＳＳ負荷を低減させるために、凝集沈殿処理で得られる上澄水の濁度を測定し、この濁度が適正値となるように水質管理が行われている。従って、高分子凝集剤については、沈殿池３の上澄水の濁度を測定し、この濁度が十分に低くなるような添加量で一定量注入が行われている。
【０００５】
【発明が解決しようとする課題】
しかし、従来の濁度による水質管理では、濾過手段の差圧上昇が著しく、濾過を継続し得なくなる場合がある。
【０００６】
即ち、高分子凝集剤が過剰添加である場合には、凝集沈殿処理で得られる上澄水の濁度は良好であっても、余剰の高分子凝集剤が濾過手段の濾材に吸着してこれを目詰まりさせることにより差圧が急上昇し、著しい場合には、濾過を継続し得なくなる場合がある。この場合、従来の上澄水の濁度による水質管理では、差圧の上昇により、濾過が困難となるまで、高分子凝集剤が過剰添加であることを知見することはできず、高分子凝集剤の添加量が適正であるか否かを判断することはできなかった。
【０００７】
上澄水のＴＯＣなどを測定して高分子凝集剤の過剰添加を調べることも考えられるが、この方法でも適正値を知ることが難しく、高分子凝集剤が過剰添加であるか否かを判断することは困難であった。
【０００８】
本発明は、上記従来の問題点を解決し、原水に無機凝集剤と高分子凝集剤とを添加して凝集濾過処理するに当たり、高分子凝集剤の添加量を適正値に制御して濾過手段の差圧の急激な上昇を防止し、安定かつ効率的な処理を行う方法及び装置を提供することを目的とする。
【０００９】
【課題を解決するための手段】
本発明の水処理方法は、原水に無機凝集剤を添加混合し、次いで高分子凝集剤を添加混合してフロックを形成させた後、濾過手段にて濾過処理する水処理方法において、前記濾過手段に導入される水の濁度を測定し、この測定結果と、フロック形成後の原水の多孔性フィルタによる濾過性に基いて、下記 (1) 〜 (3) のようにして前記高分子凝集剤の添加量を制御することを特徴とする。
【００１０】
本発明の水処理装置は、原水に無機凝集剤を添加して凝集処理する第１の凝集処理手段と、該第１の凝集処理手段の処理水に高分子凝集剤を添加して凝集処理する第２の凝集処理手段と、該第２の凝集処理手段の処理水を濾過する濾過手段とを備えてなる水処理装置において、該第２の凝集処理手段の処理水の一部を分取して濾過する多孔性フィルタと、前記濾過手段に導入される水の濁度を測定する手段と、この測定結果と、該多孔性フィルタにおける濾過性に基いて、下記 (1) 〜 (3) のようにして前記高分子凝集剤の添加量を制御する制御手段とを設けたことを特徴とする。
【００１１】
(1) 濾過手段に導入される水の濁度が適正値であり、多孔性フィルタによる濾過性が悪い場合：高分子凝集剤が過剰添加であるため、高分子凝集剤の添加量を低減する。
(2) 濾過手段に導入される水の濁度が高く、多孔性フィルタによる濾過性が悪い場合：高分子凝集剤が過少添加であるため、高分子凝集剤の添加量を増加させる。
(3) 濾過手段に導入される水の濁度が適正値であり、多孔性フィルタによる濾過性が適正である場合：高分子凝集剤は適正添加量であるため、そのままの添加量を維持する。
【００１２】
本発明では、高分子凝集剤を添加してフロックを形成させた後の水を多孔性フィルタで濾過し、このときの濾過性、例えば所定量の該水を濾過するのに要する時間（濾過時間）を調べる。高分子凝集剤が過剰添加であると、図３に示す如く、高分子凝集剤が適正添加である場合の濾過時間（以下「適正濾過時間」と称す場合がある。）よりも、この濾過時間が長くなるため、この濾過時間に基いて高分子凝集剤の添加量制御を行い、適正濾過時間よりも濾過時間が長くなる傾向にある場合には、高分子凝集剤の添加量を低減させる。
【００１３】
本発明において、多孔性フィルタによる濾過性としては、ＳＤＩ（＝ＦＩ）値、ＭＦ値などの指標を用いることができる。ＳＤＩ値、ＭＦ値はＲＯ膜給水の清澄度を表す指標として提案されたもので、通常は細孔径０．４５μｍ、直径４７ｍｍの精密濾過膜を用いて測定される数値である。
【００１４】
ＳＤＩ値は、２１０ｋＰａの操作圧で、まず最初の５００ｍＬが透過する時間ｔ１（秒）を測定し、次に加圧を開始してから１５分後よりさらに５００ｍＬが透過される時間ｔ２（秒）を測定し、次式で計算される値となる。
ＳＤＩ＝［（１−ｔ１／ｔ２）×１００］／１５
【００１５】
ＭＦ値は、５１ｋＰａの操作圧で５００ｍＬが透過する時間ｔ３（秒）を測定し、次式で計算される値となる。
ＭＦ＝（μ２５／μ）ｔ３
ここで、μ２５は２５℃の水の粘度であり、μは測定で使用された水の粘度を表し、簡略的にμ２５／μ＝１とされる場合がある。
【００１６】
特に自動ＳＤＩ測定装置（全自動フィルタ濾過時間測定器）を用いることにより、自動的にＳＤＩ値を求めることができ、測定精度を高めて（例えば１５分間隔）、高分子凝集剤添加量の制御を頻繁に行って、高分子凝集剤添加量を適正値に保つことが可能となる。
【００１７】
なお、高分子凝集剤の過少添加の場合にも多孔性フィルタによる濾過性が悪くなり、濾過時間が長くなるため、濾過性の低下が高分子凝集剤の過少添加によるものか高分子凝集剤の過剰添加によるものかを判断するために、本発明においては、濾過手段に導入される水の濁度を測定し、この測定結果と、多孔性フィルタによる濾過性とに基いて、例えば下記のようにして高分子凝集剤の添加量を制御する。
【００１８】
(1) 濾過手段に導入される水の濁度が適正値であり、多孔性フィルタによる濾過時間が適正濾過時間よりも長い場合：高分子凝集剤が過剰添加であるため、高分子凝集剤の添加量を低減する。
(2) 濾過手段に導入される水の濁度が高く、多孔性フィルタによる濾過時間が適正濾過時間よりも長い場合：高分子凝集剤が過少添加であるため、高分子凝集剤の添加量を増加させる。
(3) 濾過手段に導入される水の濁度が適正値であり、多孔性フィルタによる濾過時間も適正値である場合：高分子凝集剤は適正添加量であるため、そのままの添加量を維持する。
【００１９】
なお、上記(1)〜(3)において、濾過時間の代りに、後述の単位時間当たりの濾過量を求めても良い。
【００２０】
このようにして、高分子凝集剤添加量を制御することにより、高分子凝集剤の過剰添加による濾過手段の目詰りを効果的に防止することができ、これにより、長期にわたり、濾過手段の差圧上昇を防止して濾過手段の濾過性能を高く維持することができる。また、濾過手段の逆洗頻度を低減することができ、運転継続時間を延長して、処理効率を高めることができると共に、濾過手段の劣化を防止して寿命を延長させることができる。
【００２１】
【発明の実施の形態】
以下、図面を参照して本発明の実施の形態を詳細に説明する。
【００２２】
図１は本発明の水処理方法及び水処理装置の実施の形態を示す系統図である。
【００２３】
図１では、原水に無機凝集剤を添加して第１凝集槽１で凝集処理した後、高分子凝集剤を添加して第２凝集槽２で凝集処理し、この凝集処理水を沈殿池３で沈殿分離して得られた上澄水を濾過手段である濾過器４で濾過するに当たり、この上澄水の濾過性に基いて高分子凝集剤の添加量制御を行う。
【００２４】
即ち、沈殿池３の上澄水の一部を分取して濾過時間測定器５にて多孔性フィルタによる濾過時間を測定する。この測定値を演算器６にて適正濾過時間と比較演算し、この演算結果に基いて高分子凝集剤注入制御器７に制御信号を出力し、高分子凝集剤の添加量の制御を行う。
【００２５】
このような制御において、適正な高分子凝集剤添加量における濾過時間、即ち適正濾過時間は、後述の実験例に示すように予め実験を行うことにより、適正な高分子凝集剤添加量を調べ、この高分子凝集剤添加量における濾過時間を測定しておけば良い。
【００２６】
凝集沈殿上澄水の濾過性としては、この上澄水の一定量を採取し、これを多孔性フィルタで濾過したときの濾過時間又は上澄水を濾過したときの単位時間当たりの濾過量を測定するのが簡便である。
【００２７】
この多孔性フィルタとしては、孔径０．４５〜０．８μｍ程度の精密濾過（ＭＦ）膜等を用いることができるが、何らこれに限定されるものではない。
【００２８】
このような多孔性フィルタを用い、適正な高分子凝集剤添加量のときの濾過量（以下「適正濾過量」と称す場合がある。）又は濾過時間と、現在の濾過量又は濾過時間とを比較し、濾過量が低いか低下傾向にある場合、或いは濾過時間が長いか増加傾向にある場合には、高分子凝集剤添加量が過剰であると判断して高分子凝集剤添加量を低減する。
【００２９】
この低減の度合は、常に一定の減少割合であっても良く、適正濾過量又は適正濾過時間との差の大小に応じて調整しても良い。
【００３０】
なお、前述の如く、高分子凝集剤の過少添加の場合にも多孔性フィルタによる濾過性が悪くなるため、濾過性の低下が高分子凝集剤の過少添加によるものか高分子凝集剤の過剰添加によるものかを判断するために、本発明においては、濾過器に導入される水の濁度を測定し、この測定結果と、多孔性フィルタによる濾過性とに基いて高分子凝集剤の添加量を制御する。
【００３１】
濾過性の測定頻度は特に制限はないが、濾過性に基く制御により高分子凝集剤添加量を適正に維持するためには、制御の間隔が短い方が良く、一般的には３時間以下、特に１〜２時間程度とするのが好ましい。
【００３２】
前述の如く、自動ＳＤＩ測定装置を用いることにより、自動的にＳＤＩ値を求めることができ、測定頻度を高めて（例えば１５分間隔）、高分子凝集剤添加量の制御を頻繁に行って高分子凝集剤添加量を適正値に保つことが可能となるので好ましい。
【００３３】
なお、図１は、本発明の実施の形態の一例を示すものであって、本発明はその要旨を超えない限り、何ら図示のものに限定されるものではない。
【００３４】
例えば、図１では、無機凝集剤及び高分子凝集剤を添加した後の凝集処理水を沈殿池で沈殿分離した上澄水を濾過器で濾過しているが、これに限らず、凝集処理水を加圧浮上処理した後濾過器で濾過処理しても良く、また、凝集処理水を直接濾過器で濾過処理しても良い。ただし、濾過器の差圧の上昇を防止する点からは、凝集処理水を沈殿分離した後濾過器で濾過処理することが好ましい。
【００３５】
濾過器としては特に制限はなく、砂濾過器、二層濾過器等を用いることができる。また、濾過器のかわりに上水処理場等において使用される濾過池を用いることができる。濾過方式としても特に制限はなく、減圧方式、加圧方式等のいずれであっても良い。
【００３６】
本発明によれば、高分子凝集剤を適正な添加量で添加することができ、高分子凝集剤の過剰添加による濾過器の急激な差圧上昇を長期にわたり有効に防止することができる。
【００３７】
【実施例】
以下に実験例、実施例及び比較例を挙げて本発明をより具体的に説明する。
【００３８】
実験例１
濁度５度の原水に、ＰＡＣを５０ｍｇ／Ｌ（Ａｌ２Ｏ３として１０重量％）添加して撹拌した後、ノニオン系高分子凝集剤をそれぞれ０．２、０．１、０．０５ｍｇ／Ｌ添加して凝集沈殿処理して上澄水を得た。この上澄水の濁度は０．５度であった。
【００３９】
この上澄水を二層濾過器（アンスラサイトφ０．８ｍｍ，４００ｍｍ高さ、砂φ０．６ｍｍ，４００ｍ高さ）にＬＶ＝１０ｍ／ｈｒで通水した。このときの濾過器の差圧及び濾過水濁度の経時変化は図４，５に示す通りであった。
【００４０】
また、凝集沈殿上澄水１００ｍＬを多孔性フィルタ（φ４７ｍｍ、孔径０．４５μｍのＣＡ（酢酸セルロース）系ＭＦ膜）で濾過したときの濾過時間と高分子凝集剤添加量との関係は図６に示す通りであった。
【００４１】
この実験結果から、高分子凝集剤の適正添加量は濾過器の差圧上昇速度が遅く、濾過水濁度も長期にわたって低くおさえることができる０．０５ｍｇ／Ｌであると判断され、また、このときの凝集沈殿上澄水１００ｍＬの濾過に要する濾過時間は６０秒であることが確認された。
【００４２】
なお、濾過を継続することにより、濾過水濁度が所定時間後に上昇するのは、濾過器における高分子凝集剤の目詰まりにより濾過圧力が上昇したために、濁質が濾過水側へ漏れ出たことによるものである。
【００４３】
実施例１
図１に示す本発明の方法に従って、原水の凝集沈殿処理を行った。
【００４４】
実験例１で処理したものと同様の濁度５度の原水にＰＡＣ５０ｍｇ／Ｌを注入して第１凝集槽１で凝集処理した後、ノニオン系高分子凝集剤を０．２ｍｇ／Ｌ添加して第２凝集槽２で凝集処理し、沈殿池３の上澄水を実験例１で用いたものと同様の二層濾過器４にＬＶ＝１０ｍ／ｈｒで通水した。
【００４５】
濾過時間測定器５の濾過時間測定用多孔性フィルタとしては、φ４７ｍｍ，孔径０．４５μｍのＣＡ系ＭＦ膜を用い、沈殿池３の上澄水１００ｍＬを採取して濾過時間を測定した。なお、図示はしないが、沈殿池３の上澄水の濁度を測定する濁度計を設けた。
【００４６】
運転開始から２時間後の沈殿池３の上澄水の濾過時間は適正濾過時間の２倍の約１２０秒となったため、高分子凝集剤添加量を３０％低減させた。更に、２時間後の上澄水の濾過時間は適正濾過時間の１．５倍であったため、更に高分子凝集剤添加量を３０％低減させた。なお、この間、沈殿池３の上澄水の濁度は、１度以下の適正な濁度に維持されていた。
【００４７】
その後、同様に２時間毎に沈殿池３の上澄水の濾過時間を測定し、適正濾過時間に近づくように、上澄水の濁度が１度を超えない範囲で徐々に高分子凝集剤添加量を低減させ、上澄水の濁度が上昇傾向にある場合には、高分子凝集剤添加量を増加させるようにして、高分子凝集剤添加量の制御を行った。
【００４８】
この結果、濾過器の差圧及び得られた濾過水の濁度の経時変化は図７（ａ），（ｂ）に示す通りであった。
【００４９】
比較例１
高分子凝集剤の添加量制御を行わず、高分子凝集剤を０．２ｍｇ／Ｌの一定量注入としたこと以外は実施例１と同様にして原水の凝集濾過処理を行い、このときの濾過器の差圧及び得られた濾過水の濁度の経時変化を図８（ａ），（ｂ）に示した。
【００５０】
これらの結果から、高分子凝集剤添加量の制御を行わなかった比較例１では２４時間程度で濾過器差圧が規定値を超えて濾過不良となったが、沈殿池上澄水の濾過時間を適正濾過時間と比較しながら高分子凝集剤添加量を制御した実施例１では、濾過器の差圧及び濾過水濁度共に、４８時間程度、規定値を維持することができ、濾過継続時間を大幅に延長することができることがわかる。
【００５１】
【発明の効果】
以上詳述した通り、本発明の水処理方法及び水処理装置によれば、原水に無機凝集剤と高分子凝集剤とを添加して凝集濾過処理するに当たり、高分子凝集剤の添加量を適正値に制御して濾過器の差圧の急激な上昇を防止し、安定かつ効率的な処理を行うことができる。
【図面の簡単な説明】
【図１】本発明の水処理方法及び水処理装置の実施の形態を示す系統図である。
【図２】従来法を示す系統図である。
【図３】高分子凝集剤添加量と濾過時間との関係を示すグラフである。
【図４】実験例１における濾過器差圧の経時変化を示すグラフである。
【図５】実験例１における濾過水濁度の経時変化を示すグラフである。
【図６】実験例１における高分子凝集剤添加量と凝集沈殿上澄水の濾過時間との関係を示すグラフである。
【図７】実施例１における濾過器差圧と濾過水濁度の経時変化を示すグラフである。
【図８】比較例１における濾過器差圧と濾過水濁度の経時変化を示すグラフである。
【符号の説明】
１ 第１凝集槽
２ 第２凝集槽
３ 沈殿池
４ 濾過器
５ 濾過時間測定器
６ 演算器
７ 高分子凝集剤注入制御器[0001]
BACKGROUND OF THE INVENTION
In the present invention, the raw water is subjected to a coagulation filtration treatment by appropriately controlling the addition amount of the polymer coagulant used as a coagulant auxiliary agent for the inorganic coagulant, thereby providing a filter or a filter pond by excessive addition of the polymer coagulant. The present invention relates to a water treatment method and a water treatment apparatus that prevent a rapid increase in the differential pressure of the filtration means and improve and stabilize the treatment effect.
[0002]
[Prior art]
Conventionally, in water purification treatment and wastewater treatment, an inorganic flocculant such as polyaluminum chloride (PAC) or ferric chloride was added to the raw water to remove suspended solids (SS) in the raw water, and then coagulated and precipitated. Thereafter, the supernatant water is further subjected to gravity filtration or pressure filtration by a filtering means such as a filter or a filtration pond. In addition, for the purpose of improving coagulation sedimentation properties, nonionic or anionic polymer coagulants are used in combination with inorganic coagulants. In this case, generally, as shown in FIG. 2, after adding an inorganic flocculant to the raw water and aggregating in the first aggregating tank 1, a polymer aggregating agent is added and further agglomerated in the second aggregating tank 2. The flocs are coarsened by the treatment, and then the supernatant water is obtained by sedimentation and separation in the sedimentation basin 3, and the supernatant water is filtered by a filtering means such as a filter 4.
[0003]
Conventionally, in such a coagulation filtration process, SS is sufficiently precipitated and separated in the coagulation sedimentation process prior to the filtration process, and the SS load on the filtration means is reduced. It is desirable in terms of maintaining performance, reducing the frequency of backwashing of the filtering means and thereby improving operating efficiency, extending the life of the filtering means, and the like.
[0004]
Conventionally, in order to reduce the SS load on the filtration means, the turbidity of the supernatant water obtained by the coagulation sedimentation treatment is measured, and water quality management is performed so that the turbidity becomes an appropriate value. Therefore, for the polymer flocculant, the turbidity of the supernatant water of the sedimentation basin 3 is measured, and a fixed amount is injected in such an amount that the turbidity becomes sufficiently low.
[0005]
[Problems to be solved by the invention]
However, in the conventional water quality management by turbidity, the differential pressure of the filtration means is remarkably increased, and the filtration may not be continued.
[0006]
That is, when the polymer flocculant is excessively added, even if the turbidity of the supernatant water obtained by the coagulation sedimentation treatment is good, the surplus polymer flocculant is adsorbed on the filter medium of the filtration means and removed. When the pressure is clogged, the differential pressure rises rapidly. In the case where the pressure is significant, the filtration may not be continued. In this case, in the conventional water quality management based on the turbidity of the supernatant water, it is impossible to know that the polymer flocculant is excessively added until the filtration becomes difficult due to the increase in the differential pressure. It was not possible to judge whether or not the amount added was appropriate.
[0007]
Although it is conceivable to investigate the excessive addition of the polymer flocculant by measuring the TOC of the supernatant water, it is difficult to know the appropriate value even with this method, and it is judged whether the polymer flocculant is excessively added. It was difficult.
[0008]
The present invention solves the above-mentioned conventional problems, and when adding an inorganic flocculant and a polymer flocculant to raw water and subjecting it to a flocculant filtration treatment, the amount of the polymer flocculant added is controlled to an appropriate value to filter means. It is an object of the present invention to provide a method and apparatus for preventing a rapid increase in the differential pressure of the gas and performing stable and efficient processing.
[0009]
[Means for Solving the Problems]
The water treatment method of the present invention is the water treatment method in which an inorganic flocculant is added to and mixed with raw water, and then a polymer flocculant is added and mixed to form a floc, followed by filtration with a filtration means. the turbidity of the water introduced was measured, and this measurement result, based on the filtration due to the porous filter raw water after flocculation, the following (1) to the polymer flocculant as described (3) The addition amount of is controlled.
[0010]
The water treatment apparatus of the present invention performs a flocculation treatment by adding a first flocculation treatment means for adding an inorganic flocculant to raw water and performing a flocculation treatment, and a polymer flocculant in the treated water of the first flocculation treatment means. In a water treatment apparatus comprising a second agglomeration treatment means and a filtration means for filtering the treated water of the second agglomeration treatment means, a part of the treated water of the second agglomeration treatment means is fractionated. a porous filter for filtering Te, means for measuring the turbidity of the water introduced into the filtering means, and the measurement result, based on the filterability of the porous filter, the following (1) to (3) Thus, a control means for controlling the amount of the polymer flocculant added is provided.
[0011]
(1) When the turbidity of water introduced into the filtration means is an appropriate value and the filterability by the porous filter is poor: The polymer flocculant is excessively added, so the amount of polymer flocculant added is reduced .
(2) When the turbidity of water introduced into the filtration means is high and the filterability by the porous filter is poor: Since the polymer flocculant is added in an excessive amount, the addition amount of the polymer flocculant is increased.
(3) When the turbidity of water introduced into the filtration means is an appropriate value and the filterability by the porous filter is appropriate: Since the polymer flocculant is the appropriate addition amount, the addition amount is maintained as it is .
[0012]
In the present invention, the water after forming the floc by adding the polymer flocculant is filtered with a porous filter, and the filterability at this time, for example, the time required to filter a predetermined amount of the water (filtration time) ) When the polymer flocculant is excessively added, as shown in FIG. 3, the filtration time is longer than the filtration time when the polymer flocculant is properly added (hereinafter sometimes referred to as “appropriate filtration time”). Therefore, the addition amount of the polymer flocculant is controlled based on this filtration time, and when the filtration time tends to be longer than the proper filtration time, the addition amount of the polymer flocculant is reduced.
[0013]
In the present invention, as the filterability by porous filter, SDI (= FI) value, can be used metrics such as MF value. The SDI value and MF value have been proposed as an index representing the clarity of RO membrane water supply, and are usually numerical values measured using a microfiltration membrane having a pore diameter of 0.45 μm and a diameter of 47 mm.
[0014]
The SDI value is an operating pressure of 210 kPa, and firstly, the time t 1 (second) through which 500 mL passes is measured, and then the time t 2 (at which 500 mL passes through after 15 minutes from the start of pressurization). Second) and is calculated by the following formula.
SDI = [(1-t 1 / t 2 ) × 100] / 15
[0015]
The MF value is a value calculated by the following equation by measuring time t 3 (seconds) through which 500 mL permeates at an operating pressure of 51 kPa.
MF = (μ 25 / μ) t 3
Here, μ 25 is the viscosity of water at 25 ° C., μ represents the viscosity of water used in the measurement, and may be simply set to μ 25 / μ = 1.
[0016]
In particular, by using an automatic SDI measuring device (fully automatic filter filtration time measuring device), the SDI value can be automatically obtained, and the measurement accuracy is increased (for example, every 15 minutes), and the amount of polymer flocculant added is controlled. Frequently, the amount of the polymer flocculant added can be maintained at an appropriate value.
[0017]
In addition, when the polymer flocculant is added too little, the filterability by the porous filter is deteriorated and the filtration time becomes long. Therefore, the decrease in filterability is caused by the polymer flocculant being added too little. In order to determine whether it is due to excessive addition, in the present invention, the turbidity of water introduced into the filtration means is measured, and based on this measurement result and the filterability by the porous filter, for example, a manner that controls the amount of polymeric flocculant.
[0018]
(1) When the turbidity of water introduced into the filtration means is an appropriate value and the filtration time by the porous filter is longer than the appropriate filtration time: The polymer flocculant is excessively added. Reduce the amount added.
(2) When the turbidity of water introduced into the filtration means is high and the filtration time by the porous filter is longer than the appropriate filtration time: The polymer flocculant is added too little. increase.
(3) When the turbidity of the water introduced into the filtration means is an appropriate value and the filtration time by the porous filter is also an appropriate value: Since the polymer flocculant is an appropriate addition amount, the addition amount is maintained as it is To do.
[0019]
In the above (1) to (3) , a filtration amount per unit time described later may be obtained instead of the filtration time.
[0020]
In this way, by controlling the amount of the polymer flocculant added, it is possible to effectively prevent clogging of the filtration means due to excessive addition of the polymer flocculant. The pressure rise can be prevented and the filtration performance of the filtration means can be maintained high. In addition, the frequency of backwashing of the filtering means can be reduced, the operation continuation time can be extended to improve the processing efficiency, and the life of the filtering means can be extended by preventing the deterioration of the filtering means.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0022]
FIG. 1 is a system diagram showing an embodiment of a water treatment method and a water treatment apparatus of the present invention.
[0023]
In FIG. 1, after adding an inorganic flocculant to raw water and aggregating in the first aggregating tank 1, adding a polymer aggregating agent and aggregating in the second aggregating tank 2, this agglomerated water is added to the sedimentation basin 3. When filtering the supernatant water obtained by precipitation separation in the filter 4 as a filtering means, the addition amount of the polymer flocculant is controlled based on the filterability of the supernatant water.
[0024]
That is, a part of the supernatant water of the sedimentation basin 3 is collected and the filtration time by the porous filter is measured by the filtration time measuring device 5. The measured value is compared with the appropriate filtration time by the calculator 6, and a control signal is output to the polymer flocculant injection controller 7 based on the calculation result to control the addition amount of the polymer flocculant.
[0025]
In such control, the filtration time at the appropriate polymer flocculant addition amount, that is, the proper filtration time, is determined by examining the appropriate polymer flocculant addition amount by conducting an experiment in advance as shown in the experimental examples described later, What is necessary is just to measure the filtration time in this polymer flocculent addition amount.
[0026]
As the filterability of the coagulated sediment supernatant water, a certain amount of this supernatant water is collected, and the filtration time when it is filtered through a porous filter or the filtration amount per unit time when the supernatant water is filtered is measured. Is simple.
[0027]
As the porous filter, a microfiltration (MF) membrane having a pore diameter of about 0.45 to 0.8 μm can be used, but the present invention is not limited to this.
[0028]
Using such a porous filter, the amount of filtration (hereinafter sometimes referred to as “appropriate filtration amount”) or filtration time when the polymer coagulant is added appropriately, or the filtration time and the current filtration amount or filtration time. In comparison, if the amount of filtration is low or tends to decrease, or if the filtration time is long or tends to increase, the amount of polymer flocculant added is judged to be excessive and the amount of polymer flocculant added is reduced. To do.
[0029]
The degree of this reduction may always be a constant reduction rate, or may be adjusted according to the difference between the appropriate filtration amount or the appropriate filtration time.
[0030]
As described above, even when the polymer flocculant is excessively added, the filterability by the porous filter is deteriorated. Therefore, the decrease in filterability is due to the excessive addition of the polymer flocculant or excessive addition of the polymer flocculant. In the present invention, the turbidity of the water introduced into the filter is measured, and the amount of the polymer flocculant added based on the measurement result and the filterability of the porous filter. that control.
[0031]
The measurement frequency of filterability is not particularly limited, but in order to properly maintain the polymer flocculant addition amount by control based on filterability, it is better that the control interval is short, generally 3 hours or less, In particular, it is preferably about 1 to 2 hours.
[0032]
As described above, by using an automatic SDI measuring device, the SDI value can be automatically obtained, the measurement frequency is increased (for example, every 15 minutes), and the amount of polymer flocculant added is frequently controlled to increase the SDI value. This is preferable because the addition amount of the molecular flocculant can be maintained at an appropriate value.
[0033]
FIG. 1 shows an example of an embodiment of the present invention, and the present invention is not limited to the illustrated one as long as the gist thereof is not exceeded.
[0034]
For example, in FIG. 1, the supernatant water obtained by precipitating and separating the agglomerated water after adding the inorganic flocculant and the polymer flocculant in the sedimentation basin is filtered by a filter. After the pressure levitation treatment, it may be filtered with a filter, or the flocculated water may be filtered directly with a filter. However, from the standpoint of preventing an increase in the differential pressure of the filter, it is preferable to perform a filtration treatment with a filter after the flocculated water is precipitated and separated.
[0035]
There is no restriction | limiting in particular as a filter, A sand filter, a two-layer filter, etc. can be used. Moreover, the filtration pond used in a water treatment plant etc. can be used instead of a filter. There is no restriction | limiting in particular also as a filtration system, Any of a pressure reduction system, a pressurization system, etc. may be sufficient.
[0036]
ADVANTAGE OF THE INVENTION According to this invention, a polymer flocculent can be added with an appropriate addition amount, and the rapid pressure difference rise of a filter by excessive addition of a polymer flocculant can be prevented effectively over a long period of time.
[0037]
【Example】
Hereinafter, the present invention will be described in more detail with reference to experimental examples, examples and comparative examples.
[0038]
Experimental example 1
After adding 50 mg / L of PAC (10 wt% as Al 2 O 3 ) to raw water with a turbidity of 5 ° C., the nonionic polymer flocculant was added at 0.2, 0.1, 0.05 mg / L, respectively. L was added and coagulation sedimentation treatment was performed to obtain supernatant water. The turbidity of this supernatant water was 0.5 degree.
[0039]
This supernatant water was passed through a two-layer filter (anthracite φ0.8 mm, 400 mm height, sand φ0.6 mm, 400 m height) at LV = 10 m / hr. The time-dependent changes in the differential pressure and filtered water turbidity of the filter at this time were as shown in FIGS.
[0040]
FIG. 6 shows the relationship between the filtration time and the amount of the polymer flocculant added when 100 mL of the coagulated sediment supernatant water is filtered through a porous filter (CA (cellulose acetate) MF membrane having a diameter of 47 mm and a pore diameter of 0.45 μm). It was street.
[0041]
From this experimental result, it is determined that the appropriate amount of the polymer flocculant is 0.05 mg / L, which allows the rate of increase in the differential pressure of the filter to be slow and the filtration turbidity to be kept low over a long period of time. It was confirmed that the filtration time required for filtration of 100 mL of the coagulation sediment supernatant was 60 seconds.
[0042]
In addition, the filtration water turbidity increases after a predetermined time by continuing the filtration because the filtration pressure increased due to clogging of the polymer flocculant in the filter, and the turbidity leaked to the filtered water side. It is because.
[0043]
Example 1
In accordance with the method of the present invention shown in FIG. 1, the raw water was coagulated and settled.
[0044]
After injecting PAC 50 mg / L into raw water having a turbidity of 5 degrees similar to that treated in Experimental Example 1 and aggregating in the first aggregating tank 1, 0.2 mg / L of nonionic polymer flocculant was added. The flocculation treatment was performed in the second flocculation tank 2, and the supernatant water of the sedimentation basin 3 was passed through the two-layer filter 4 similar to that used in Experimental Example 1 at LV = 10 m / hr.
[0045]
As a porous filter for measuring the filtration time of the filtration time measuring device 5, a CA-based MF membrane having a diameter of 47 mm and a pore diameter of 0.45 μm was used, and 100 mL of the supernatant water of the sedimentation basin 3 was collected to measure the filtration time. Although not shown, a turbidimeter for measuring the turbidity of the supernatant water of the sedimentation tank 3 was provided.
[0046]
Since the filtration time of the supernatant water of the sedimentation basin 3 after 2 hours from the start of the operation was about 120 seconds, which is twice the appropriate filtration time, the amount of the polymer flocculant added was reduced by 30%. Furthermore, since the filtration time of the supernatant water after 2 hours was 1.5 times the appropriate filtration time, the addition amount of the polymer flocculant was further reduced by 30%. During this time, the turbidity of the supernatant water of the sedimentation basin 3 was maintained at an appropriate turbidity of 1 degree or less.
[0047]
Thereafter, similarly, the filtration time of the supernatant water of the sedimentation basin 3 is measured every 2 hours, and the amount of the polymer flocculant is gradually added so that the turbidity of the supernatant water does not exceed 1 degree so as to approach the appropriate filtration time. When the turbidity of the supernatant water tends to increase, the amount of the polymer flocculant added was controlled so as to increase the amount of the polymer flocculant added.
[0048]
As a result, the change over time in the differential pressure of the filter and the turbidity of the obtained filtrate was as shown in FIGS. 7 (a) and 7 (b).
[0049]
Comparative Example 1
The raw water was coagulated and filtered in the same manner as in Example 1 except that the addition amount of the polymer flocculant was not controlled and the polymer flocculant was given at a fixed amount of 0.2 mg / L. Changes in the pressure difference of the vessel and the turbidity of the obtained filtered water are shown in FIGS. 8 (a) and 8 (b).
[0050]
From these results, in Comparative Example 1 in which the amount of the polymer flocculant added was not controlled, the filter differential pressure exceeded the specified value in about 24 hours, resulting in poor filtration. In Example 1 in which the amount of the polymer flocculant added was controlled while comparing with the filtration time, both the differential pressure of the filter and the filtered water turbidity can be maintained at the specified values for about 48 hours, greatly increasing the filtration duration. It can be seen that it can be extended.
[0051]
【The invention's effect】
As described above in detail, according to the water treatment method and the water treatment apparatus of the present invention, when adding the inorganic flocculant and the polymer flocculant to the raw water and performing the flocculant filtration treatment, the addition amount of the polymer flocculant is appropriate. By controlling the value, a rapid increase in the differential pressure of the filter can be prevented, and stable and efficient processing can be performed.
[Brief description of the drawings]
FIG. 1 is a system diagram showing an embodiment of a water treatment method and a water treatment apparatus of the present invention.
FIG. 2 is a system diagram showing a conventional method.
FIG. 3 is a graph showing the relationship between the amount of polymer flocculant added and the filtration time.
4 is a graph showing a change with time of a filter differential pressure in Experimental Example 1. FIG.
FIG. 5 is a graph showing the change with time of filtered water turbidity in Experimental Example 1.
6 is a graph showing the relationship between the amount of polymer flocculant added and the filtration time of the coagulated sediment supernatant in Experimental Example 1. FIG.
7 is a graph showing temporal changes in filter differential pressure and filtered water turbidity in Example 1. FIG.
8 is a graph showing changes over time in filter differential pressure and filtered water turbidity in Comparative Example 1. FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 1st flocculation tank 2 2nd flocculation tank 3 sedimentation basin 4 filter 5 filtration time measuring device 6 calculator 7 polymer flocculant injection controller
Claims (3)
前記濾過手段に導入される水の濁度を測定し、この測定結果と、フロック形成後の原水の多孔性フィルタによる濾過性に基いて、下記 (1) 〜 (3) のようにして前記高分子凝集剤の添加量を制御することを特徴とする水処理方法。
(1) 濾過手段に導入される水の濁度が適正値であり、多孔性フィルタによる濾過性が悪い場合：高分子凝集剤が過剰添加であるため、高分子凝集剤の添加量を低減する。
(2) 濾過手段に導入される水の濁度が高く、多孔性フィルタによる濾過性が悪い場合：高分子凝集剤が過少添加であるため、高分子凝集剤の添加量を増加させる。
(3) 濾過手段に導入される水の濁度が適正値であり、多孔性フィルタによる濾過性が適正である場合：高分子凝集剤は適正添加量であるため、そのままの添加量を維持する。 In a water treatment method in which an inorganic flocculant is added to and mixed with raw water, and then a polymer flocculant is added and mixed to form a floc, followed by filtration with a filtering means.
The measured turbidity of water introduced into the filtering means, and the measurement result, based on the filtration due to the porous filter raw water after flocculation, the high as follows (1) to (3) A water treatment method characterized by controlling the amount of molecular flocculant added.
(1) When the turbidity of water introduced into the filtration means is an appropriate value and the filterability by the porous filter is poor: The polymer flocculant is excessively added, so the amount of polymer flocculant added is reduced .
(2) When the turbidity of water introduced into the filtration means is high and the filterability by the porous filter is poor: Since the polymer flocculant is added in an excessive amount, the addition amount of the polymer flocculant is increased.
(3) When the turbidity of water introduced into the filtration means is an appropriate value and the filterability by the porous filter is appropriate: Since the polymer flocculant is the appropriate addition amount, the addition amount is maintained as it is .
該第１の凝集処理手段の処理水に高分子凝集剤を添加して凝集処理する第２の凝集処理手段と、
該第２の凝集処理手段の処理水を濾過する濾過手段とを備えてなる水処理装置において、
該第２の凝集処理手段の処理水の一部を分取して濾過する多孔性フィルタと、
前記濾過手段に導入される水の濁度を測定する手段と、
この測定結果と、該多孔性フィルタにおける濾過性に基いて、下記 (1) 〜 (3) のようにして前記高分子凝集剤の添加量を制御する制御手段とを設けたことを特徴とする水処理装置。
(1) 濾過手段に導入される水の濁度が適正値であり、多孔性フィルタによる濾過性が悪い場合：高分子凝集剤が過剰添加であるため、高分子凝集剤の添加量を低減する。
(2) 濾過手段に導入される水の濁度が高く、多孔性フィルタによる濾過性が悪い場合：高分子凝集剤が過少添加であるため、高分子凝集剤の添加量を増加させる。
(3) 濾過手段に導入される水の濁度が適正値であり、多孔性フィルタによる濾過性が適正である場合：高分子凝集剤は適正添加量であるため、そのままの添加量を維持する。 A first coagulation treatment means for adding an inorganic coagulant to the raw water and coagulating it;
A second aggregating treatment means for adding a polymer flocculant to the treated water of the first aggregating treatment means to agglomerate;
A water treatment apparatus comprising a filtration means for filtering the treated water of the second agglomeration treatment means,
A porous filter for separating and filtering a part of the treated water of the second aggregating treatment means;
Means for measuring the turbidity of the water introduced into the filtration means;
And this measurement result, based on the filterability of the porous filter, characterized in that a control means for controlling the amount of the polymer flocculant as described below (1) to (3) Water treatment equipment.
(1) When the turbidity of water introduced into the filtration means is an appropriate value and the filterability by the porous filter is poor: The polymer flocculant is excessively added, so the amount of polymer flocculant added is reduced .
(2) When the turbidity of water introduced into the filtration means is high and the filterability by the porous filter is poor: Since the polymer flocculant is added in an excessive amount, the addition amount of the polymer flocculant is increased.
(3) When the turbidity of water introduced into the filtration means is an appropriate value and the filterability by the porous filter is appropriate: Since the polymer flocculant is the appropriate addition amount, the addition amount is maintained as it is .
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| JP6105220B2 (en) * | 2011-07-12 | 2017-03-29 | 高砂熱学工業株式会社 | Treatment method of flushing waste water from piping system of equipment with galvanized steel pipes |
| JP5925005B2 (en) * | 2012-03-24 | 2016-05-25 | 水道機工株式会社 | Coagulation precipitation filtration system |
| JP5993605B2 (en) * | 2012-04-27 | 2016-09-14 | 水ｉｎｇ株式会社 | Flocculant evaluation method and flocculant processing apparatus |
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| JPH06233903A (en) * | 1993-02-10 | 1994-08-23 | Kawasaki Steel Corp | Method for continuously monitoring concentration of residual suspended substance in purified treated water and apparatus therefor |
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